Direct-developing sea urchins and the evolutionary reorganization of early development
Article Abstract:
The embryo fate maps of direct-developing sea urchins (Heliocidaris erythrogramma) and indirect-developing sea urchins (H. tuberculata) were compared to understand the mechanisms of ontogenic evolution. It was seen that the loss of the larval stage in H. erythrogramma cannot simply be explained by heterochrony, or changes in the timing of ancestral developmental events, but by underlying changes in gene expression, beginning with gametogenesis, which cause major reorganizations of external and internal cell fates and altered cell-cell interactions.
Publication Name: BioEssays
Subject: Biological sciences
ISSN: 0265-9247
Year: 1992
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Ontogeny and phylogeny - revisited and reunited
Article Abstract:
Development of knowledge about heterochrony, the shift in relative time frames and in rates of dissociated developmental events, allows a reevaluation of Haeckel's recapitulation theory, widely accepted in Darwin's time but discredited in the late 19th and early 20th century as merely descriptive. A reunification of the themes of development and evolution is made possible because heterochronic events can be explained in terms of Darwinism's external mutation agents interacting with internal constraints inherent in development.
Publication Name: BioEssays
Subject: Biological sciences
ISSN: 0265-9247
Year: 1992
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Evolution of direct-developing larvae: selection vs. loss
Article Abstract:
The current hypothesis for evolution of the direct developing larval form in sea urchin Clypeaster rosaceus was examined. Results suggested that transformation of larval form has resulted in strong selection on early initiation of adult development.
Publication Name: BioEssays
Subject: Biological sciences
ISSN: 0265-9247
Year: 2007
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